Types of Solutions (13.1.1) Flashcards
• A solution is formed by the dissolution of a solute in a solvent.
• A solution is formed by the dissolution of a solute in a solvent.
• Solutions can be unsaturated, saturated, or supersaturated.
• Solutions can be unsaturated, saturated, or supersaturated.
• Like dissolves like. Polar solvents tend to dissolve ionic and polar compounds, and nonpolar solvents tend to dissolve nonpolar compounds.
• Like dissolves like. Polar solvents tend to dissolve ionic and polar compounds, and nonpolar solvents tend to dissolve nonpolar compounds.
Suppose that you do the following simple demonstration for saturation of a solution.
Step 1: Place 1 teaspoon of salt into the solution and stir. Observation: All of the salt dissolves.
Step 2: Place 1 teaspoon of salt into the solution and stir. Observation: All of the salt dissolves.
Step 3: Place 1 teaspoon of salt into the solution and stir. Observation: Some of the salt dissolves.
Step 4: Place 1 teaspoon of salt into the solution and stir. Observation: None of the salt dissolves.
Step 5: Place 1 teaspoon of salt into the solution and stir. Observation:?
Which statement best explains what happened and also predicts what will be observed in Step 5?
Salt was added to a solution in increments of 1 teaspoon each time. During Steps 1 and 2, the solution remained unsaturated. During Step 3, the solution reached its saturation point. Any salt added after Step 3 would not dissolve, including the salt from Step 5. (B)
This is a very clear and correct statement about what occurred. The solution reached its saturation point during Step 3.
Which of the following statements about a saturated solution is not true?
In a saturated solution, the solute atoms and molecules no longer change states (between dissolved and undissolved solute) because equilibrium exists. (D)
Equilibrium does exist but what does not change is the concentration of dissolved solute versus undissolved solute. Atoms and molecules are interacting, but the aggregate change in concentration is zero.
The diagram compares the moles of solute added to a solution to the concentration of the solute in the solution. The concentration of the solute in the solution is the amount of solute dissolved in the solution.
Each of the five points is associated with one of the following terms: an unsaturated solution, a saturated solution with excess undissolved solute, a supersaturated solution, the saturation point, or the solubility for the solution. Which of the following matches each term with its correct number on the graph?
Point 1: solubility; Point 2: an unsaturated solution; Point 3: the saturation point; Point 4: a saturated solution with excess undissolved solute; Point 5: a supersaturated solution (D)
Point 2 represents the portion of the curve where the solution is dissolving all of the solute that it receives, so this is an unsaturated solution. At Point 3, the graph breaks into two directions. One part continues upwards and is indicated by Point 5, which represents a supersaturated solution. To the right of Point 3 the graph is a line. Point 4 on that line represents a saturated solution with excess undissolved solute. Point 3 represents the saturation point because, after this point, any additional moles of solute that are added to the solution are not dissolved. That leaves Point 1, which is the solubility for the solution. The solubility of a specific solution (at any specific temperature) never changes.
Which of the following best describes Point 5 on the graph?
At this point, the solution is supersaturated. It has more dissolved solute (at a given temperature) than would normally be expected. (B)
Suppose that you do the following simple demonstration for saturation of a solution.
Step 1: Place 1 teaspoon of salt into the solution and stir. Observation: All of the salt dissolves.
Step 2: Place 1 teaspoon of salt into the solution and stir. Observation: All of the salt dissolves.
Step 3: Place 1 teaspoon of salt into the solution and stir. Observation: Some of the salt dissolves.
Step 4: Place 1 teaspoon of salt into the solution and stir. Observation: None of the salt dissolves.
Step 5: Place 1 teaspoon of salt into the solution and stir. Observation:?
Which statement about this demonstration is not true?
By adding the salt more slowly to the saturated solution, you can increase the concentration of dissolved salt. (D)
Look at the diagram that compares the moles of solute added to a solution to the concentration of the solute in the solution.
Three of the four answer choices below use the same value for the concentration of solute in solution. For which number point on the graph is the solute in solution different from the other three points in the choices below?
Point 2 (D)
This is the only point where the concentration of solute does not have the same value as at the other points. This question is basically asking, “Which three points have the same value for their y component?” The y-axis represents the concentration of the solute in solution. At Points 1, 3, and 4, the concentration of the solute is the same. It is equal to the value of the solute at Point 1 (on the y-axis).
Table salt is added to water in table spoon amounts. It is stirred into solution until solid salt remains on the container bottom and does not dissolve. Which statement about this demonstration is not true?
The concentration of dissolved salt increased continually as more salt was added. (D)
This was true until the saturation point was reached. Then, adding more salt did not result in an increase in the concentration of dissolved salt.
What is a saturated solution?
A saturated solution is a solution that contains the maximum possible concentration of solute (at a given temperature). (C)
Which of the following statements best summarizes the solubility of solutes in solvents?
Like dissolves like. (In other words, solutes that have similar bonding schemes to their solvents will be more soluble than solutes that have bonding arrangements different from their solvents.) (B)
This is the rule for predicting the solubility of a solute in a solvent. Generally speaking, polar solvents best dissolve polar solutes, while nonpolar solvents best dissolve nonpolar solutes.
Look at the graph that compares the moles of solute (added to a solution) to the concentration of the solute in the solution.
Assume that you are starting at Point 1 with a pure solvent. You then slowly add solute particles until you reach Point 5. Which statement best describes what is happening at each point (1 − 5) in the process?
At Point 0, the graph shows that you have a pure solvent (i.e., no solute). From Point 0 to Point 3, solute is added and dissolved. Beyond Point 3, none of the additional solute that is added is dissolved because the solution is saturated. (D)
The plot says that a pure solvent will dissolve solute until it reaches its saturation point. After that point, any solute will not be dissolved. Therefore, the concentration of dissolved solute is constant once the saturation point is reached.
